PubMed · 14359511
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
E K UNAT. 1954. [Not Available].. https://pubmed.ncbi.nlm.nih.gov/14359511/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Representational difference analysis of cDNAs (cDNA-RDA) is a sensitive subtractive hybridization technique capable of isolating rare mRNAs differentially expressed in two cell populations. cDNA-RDA can detect sequences represented at 0.0001% in the starting mRNA. By using reverse transcriptase polymerase chain reaction (PCR), cDNA-RDA also lends itself to studies in which samples are derived from limited numbers of cells. Standard cDNA-RDA protocols depend upon the presence of specific restriction enzyme sites in each cDNA, typically enzymes with four base recognition sequences. These sites are used to reduce the cDNA size range and provide primer sites for subsequent PCR amplification. Consequently, transcripts containing fewer than two of the chosen restriction sites are undetectable by cDNA-RDA. We have developed a restriction enzyme site-independent cDNA-RDA protocol called modified RDA (MRDA). We constructed MRDA test sequences from random hexamer-primed cDNA, thereby increasing the representation of mRNAs which are excluded by cDNA-RDA protocols. MRDA is also more efficient than cDNA-RDA at removing highly expressed housekeeping genes during the subtractive hybridization process, thereby allowing more efficient isolation of preferentially expressed mRNAs. Using MRDA, we isolated cDNAs differentially expressed between limited numbers of human CD4(+) naive and memory T lymphocyte subsets and skin- and gut-homing memory T cell subsets.
MR-based molecular imaging is a science in infancy. Current clinical contrast agents are often geared toward the assessment of gross physiologic function, rather than targeting specific biochemical pathways. The development of specific targeted smart contrast agents for Food and Drug Administration approval or clinical trials has only begun. The fact that MR imaging can obtain images of extremely high resolution, coupled with its ability to simultaneously assess structure and function through the use of targeted contrast agents indicates that MR will play a pivotal role in clinical molecular imaging of the future. Many of the challenges that face MR imaging and spectroscopy are inherent to all modalities in the rapidly growing field of molecular imaging. The development of smart contrast agents to report on receptor function, and to monitor gene expression or the results of gene therapy in humans is paramount. These compounds need to undergo rigorous testing to be approved for clinical use: the assessment of acute toxicity, pharmacokinetics, long-term accumulation, and subsequent chronic effects. For receptor-targeted contrast agents, the degree of receptor occupancy and the intrinsic agonist or antagonist properties of the probe that may affect normal cellular function need to be determined to avoid undesired side effects. The particular problems that face MR imaging, those of sensitivity and target specificity, need to be overcome. Signal amplification achieved through high relaxivity contrast agents containing multiple paramagnetic centers, or of larger superparamagnetic particles, is the first step in this direction. The modulation of relaxivity through oligomerization, or other modifications that cause restriction of rotational motions, shows great promise for improving the discriminative powers of MR imaging, and may permit multiple targets to be assessed simultaneously. Moreover, the introduction of smart indicators that lead to changes in spectroscopic properties will allow further discrimination to be achieved through the implementation of chemical shift or spectroscopic imaging. The growing number of MR imaging applications in this rapidly expanding field point to a bright future for MR imaging in molecular imaging.
The most important goal of structural cell biology is to elucidate the mechanisms of the processes of life. The structure of a membrane system or fibrous array, the changes in such structures over time or the localizations of enzymes relative to organelle boundaries can often illuminate associated cellular functions. To be of maximal value, structural studies should provide isotropic, 3D information about well-preserved samples at the highest possible resolution. Electron tomography can provide such information about many kinds of cells and organelles.